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Molecules 2014, 19(4), 4418-4432; doi:10.3390/molecules19044418
Article

Synthesis of Regiospecifically Fluorinated Conjugated Dienamides

, ,  and *
Received: 16 February 2014; in revised form: 22 March 2014 / Accepted: 31 March 2014 / Published: 10 April 2014
(This article belongs to the Special Issue Fluorine Chemistry)
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Abstract: Modular synthesis of regiospecifically fluorinated 2,4-diene Weinreb amides, with defined stereochemistry at both double bonds, was achieved via two sequential Julia-Kocienski olefinations. In the first step, a Z-a-fluorovinyl Weinreb amide unit with a benzothiazolylsulfanyl substituent at the allylic position was assembled. This was achieved via condensation of two primary building blocks, namely 2-(benzo[d]thiazol-2-ylsulfonyl)-2-fluoro-N-methoxy-N-methylacetamide (a Julia-Kocienski olefination reagent) and 2-(benzo[d]thiazol-2-ylthio)acetaldehyde (a bifunctional building block). This condensation was highly Z-selective and proceeded in a good 76% yield. Oxidation of benzothiazolylsulfanyl moiety furnished a second-generation Julia-Kocienski olefination reagent, which was used for the introduction of the second olefinic linkage via DBU-mediated condensations with aldehydes, to give (2Z,4E/Z)-dienamides in 50%–74% yield. Although olefinations were 4Z-selective, (2Z,4E/Z)-2-fluoro-2,4-dienamides could be readily isomerized to the corresponding 5-substituted (2Z,4E)-2-fluoro-N-methoxy-N-methylpenta-2,4-dienamides in the presence of catalytic iodine.
Keywords: fluoro dienamides; Julia-Kocienski olefination; Weinreb amide; fluoro dienes fluoro dienamides; Julia-Kocienski olefination; Weinreb amide; fluoro dienes
This is an open access article distributed under the Creative Commons Attribution License which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

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MDPI and ACS Style

Chowdhury, M.; Mandal, S.K.; Banerjee, S.; Zajc, B. Synthesis of Regiospecifically Fluorinated Conjugated Dienamides. Molecules 2014, 19, 4418-4432.

AMA Style

Chowdhury M, Mandal SK, Banerjee S, Zajc B. Synthesis of Regiospecifically Fluorinated Conjugated Dienamides. Molecules. 2014; 19(4):4418-4432.

Chicago/Turabian Style

Chowdhury, Mohammad; Mandal, Samir K.; Banerjee, Shaibal; Zajc, Barbara. 2014. "Synthesis of Regiospecifically Fluorinated Conjugated Dienamides." Molecules 19, no. 4: 4418-4432.



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